Electrical ignition apparatus for internal combustion engines



Sept. 19, 1939. F. R. F. RAMSAY 2,173,766

ELECTRICAL IGNITION APPARATUS FOR INTERNAL COMBUSTION ENGINES Filed Jan.10, 1938 Patented Sept. 19, 1939 ELECTRICAL IGNITION APPARATUS FORINTERNAL COMBUSTION ENGINES Raymond Faber Ramsay, London, England,assignor to D. Napier & Son Limited, London, England, a company of GreatBritain Application January 10, 1938, Serial No. 184,310 In GreatBritain January 20, 1937 10 Claims.

This invention relates to electrical ignition ap-, paratus for internalcombustion engines and of the kind in which means are provided tendingto prevent the electrical ignition apparatus causing interference withwireless receiving apparatus used, for example, on'the aeroplane orother vehicle on which the internal combustion engine is installed.

It has been proposed for the purpose of preventing interference withwireless receiving apparatus to interpose a resistance of the orderol10,000 ohms between the end of each high tension sparking plug lead andthe sparking plug terminal. This proposal only partially preventsinterference and in an alternative arrangement for preventinginterference more completely, a completely screened high tension systemis employed, that is to say the whole of the high tension circuitincluding the high tension sparking plug cables, the central electrodesof the sparking plugs and other parts through which the high tensioncurrent flows, are enclosed in a continuous metallic screen which isearthed, that is to say connected to the body of the engine.

This latter expedient, however, tends to cause rapid erosion of thesparking plug points due, it is believed, to theiact that the earthedscreen and the high tension cables together form in effect a condenserwhich gives to the circuit the charac ter of an oscillating circuit, andthe object of the present invention is to overcome this difiiculty andthus not only provide elimination of interference which radio signalsbut also prevent the rapid erosion of the sparking plug points.

To this end, according to the present invention, a resistance isprovided between each high tension. cable and its associated sparkingplug point in completely screened electrical ignition apparatus for aninternal combustion engine.

The value of the resistance may vary but is preferably between 100 ohmsand 4,000 ohms and in most cases should be of the order of 1,000 or1,500 ohms.

In any case this resistance may either be disposed between the end ofthe cable and the sparking plug terminal or may be disposed within thesparking plug insulator between the sparking plug terminal and theappropriate sparking plug point.

'Anarrangement according to the invention is illustrateddiagrammatically in Figure 1 of the accompanying drawing while Figure 2shows partly in cross-section a constructional arrangement incorporatinga resistance according to the in- In the circuit according to theinvention shown in Figure 1, A is the secondary winding of thetransformer of the magneto or coil type ignition apparatus of which A isthe primary winding, one end of the secondary winding A being connectedas usual to earth, that is to say to the body of the engine, which isrepresented by the conductor B. The other end of the secondary winding.is connected as usual to the arm C of a distributor 0 the variousterminals of which are connected respectively to the central electrodesof the sparking plugs of the various cylinders. In Figure 1 thedistributor is shown as having six such terminals for use with a sixcylinder engine and for the sake of simplicity the high tension cableleading from only oneof such terminals to its associated sparking plugis illustrated. In practice each terminal of the distributor would beconnected to its associated sparking plug in the manner shown for oneterminal. Thus, each ter- 'minal of the distributor is connected to oneend of a high tension cable D the other end of which is connectedthrough a resistance D of, say, 1,000 ohms to the central electrode E ofthe sparking plug F the body F 01' which is, as shown, connected toearth by being screwed into its appropriate cylinder. The high tensioncircuit is completely screened in known manner, this screeningrepresenting a capacity indicated at G.

It will be appreciated that the screening is earthed and encloses alsothe insulator and the part of the central electrode of the sparking pluglying above the body F thereof and Figure 2 shows one way in which theresistance may be arranged.

In the arrangement shown in Figure 2, the high tension cable D with theusual rubber or like insulation D is screened also in known manner by awoven metallic sheath D The end of-this cable adjacent to the sparkingplug passes into an L-sha'ped connector comprising an outer metalliccasing G containing a filling of moulded insulating material G One armof the metallic casing G is externally screwthreaded, as

to. The nipple, which is of ball-like'form, lies within a three-sidedspring clip J the sides oi which press thereon so as to make closeelectrical contact therewith and the resistance D is disposed in a borein the filling (3 at right angles to that into which the high tensioncable D projects. The lower end or the resistance D is acted upon by acap K against which bears one end of a spring K the other end of whichbears on a cap K the caps K and K being capable of slidinglongitudinally within a tubular surrounding sheath K and the arrangementbeing such that the spring K acts through the cap K to press theresistance D upwards so that its upper end makes close contact with thelower face of the spring clip J.

The device is intended for use with a sparking plug F 01' the known typeshown in which a metallic screening member F lined with insulatingmaterial 13 extends upwards from the body F of the plug and isexternally screwthreaded at its upper end to be engaged by ascrewthreaded collar L serving to draw a flange G on'the metallic casingG downwards into close contact with the upper end of the screen F".

The filling G of insulating material extends downwards beyond the flangeG, as shown, and the arrangement is such that when the device is appliedto a sparking plug as shown, the central electrode E of the'plug engagesthe lower cap K and presses it upwards somewhat against the action ofthe spring K Thus the spring K not only maintains the resistance D inclose contact with the spring clip J but also" serves to carry hightension current between the resistance D and the central electrode E ofthe sparking plug F With this construction it will be seen that completemetallic screening is provided for the high tension conductor, thisscreening extending downwards around the resistance D and the insulatorand central electrode E of the sparking plug to the body F of thesparking plug which is connected to earth.

It is to be understood that the construction adopted to provide for theinterposition of the resistance between the high tension lead and thecentral electrode of the sparking plug may vary within wide limitsaccording to requirements. the type '0! sparking plug or screeningemployed, the space which is availableior the connection between thehigh tension lead and the central electrode of the sparking plug andother requirements. Further, if desired the resistance may be arrangedin the length of the high tension lead within the screening, or may bearranged within the insulator oi the sparking plug or an extension orthis insulator.

What I claim as my invention and desire to secure by Letters Patent is:

1. Electrical ignition apparatus for internal combustion engines,including at least one high tension cable, a sparking plug to which oneend of the cable is connected, a source of high tension current to whichthe other end 01' the cable is connected, a continuous earthed metallicscreen enclosing the high tension circuit, and a resistance of betweenand 4,000 ohms interposed between the high tension cable and thesparking plug point.

2. Electrical ignition apparatus for internal combustion engines,including at least one high tension cable, a sparking plug to which oneend of the cable is connected, a source of high tension current to whichthe other end of the cable is connected, a continuous earthed metallicscreen enclosing the high tension circuit, and a resistance of between500 and 1,500 ohms interposed between the highv tension cable and thesparking plug point; r

3. Electrical ignition apparatus for internal combustion enginesincluding at least one high tension cable, a source of high tensioncurrent to which one end of the cable is connected, a sparking plug, acontinuous earthed metallic screen enclosing the high tension circuit,and means including a resistance of between 100 and 4,000 ohms forconnecting the other end oi. the high tension lead to the outer end ofthe central electrode oi the sparking plug.

4. Electrical ignition apparatus for. internal combustion enginesincluding at leastone high tension cable, a source of high tensioncurrent to which one end of the cable is connected, 9. sparking plug, acontinuous earthed metallic screen enclosing the high tension circuit,and means including a resistance of between 1,000 and 1,500 ohms forconnecting the other end of the high tension lead to the outer end ofthe central electrode of the sparking plug.

5. Electrical ignition apparatus for internal combustion enginesincluding at least one high tension cable, a source of high tensioncurrent to which one end of the cable is connected, 8. sparking plug, ametallic screen for the high tension cable and means for connecting theother end of the cable to the sparking plug comprising a coupling memberincluding a metallic casing, a filling of insulating material within thecasing having a bore therethrough, means for clamping one end of thecasing to the end of the cable screen, means for connecting the otherend of the casing to a metallic body which screens the central electrodeof the sparking plug, a resistance of between 100 and 4,000 ohms withinthe bore of the filling, means for connecting one end of the resistanceelectrically to the high tension cable, and means for connecting theother end of the resistance electrically to the central electrode of thesparking plug.

6. Electrical ignition apparatus for internal combustion enginesincluding at least one high tension cable, a source of high tensioncurrent to which one end of the cable is connected, a sparking plug, ametallic screen for the high tension cable and means for connecting theother end of the cable to the sparking plug comprising a coupling memberincluding a metallic casing, a filling of insulating material within thecasing having a bore therethrough, means for clamping one end 01' thecasing to the end of the cable screen, means for connecting the otherend of the casing to a metallic body which screens the central electrodeof the sparking plug, a resistance of between 500 and 1,500 ohms withinthe bore oTthe filling, means for connecting one end of the resistanceelectrically to the high tension cable, and means for connecting theother endoi the resistance electrically to the central electrode of thesparking plug.

'7. Electrical ignition apparatus for internal combustion enginesincluding at least one high tension cable, a source of high tensioncurrent the casing to a metallic body which screens the 75 centralelectrode of the sparking plug, a metallic member within the bore in thefilling to which the end of the high tension cable is electricallyconnected, a resistance of between 100 and 4,000 ohms aranged in thisbore with one end engaging this metallic member, a spring within thebore one end of which acts on the other end of the resistance to pressit into contact with the metallic member, and a contact member actedupon by the'other end of the spring and adapted the casing to the end ofthe cable screen, means for connecting the other end of the casing to ametallic screen surrounding the insulator o! the sparking plug, aresistance of between 100 and 4,000 ohms within the bore oi the filling,means for connecting one end of the resistance elec-' trically to thehigh tension cable, and means for connecting the other end or theresistance electrically to the central electrode of the sparking P us.

9. A connector for coupling a screened high tension cable in theignition circuit of an internal combustion engine to a sparking plugcomprising a metallic casing, a filling of insulating material withinthe casing having a bore therethrough, means for clamping one end of thecasing to the end of the cable screen, means for connecting the otherend of the casing to the metallic body of the sparking plug, aresistance of between 100 and 4,000 ohms within the bore in the-filling, means for connecting one end or .the resistance electricallyto the high tension cable, and means for connecting the other end of theresistance electrically to the central electrode of the sparking plug.

10. A connector for coupling a screened high tension cable in theignition circuit of an internal combustion engine to a sparking plugcomprising a metallic casing, a filling of insulating material withinthe casing having a bore therethrough, means for clamping one end of thecasing to the end of the cable screen, means for connecting the otherend of the casing to the metallic body of a sparking plug, a resistanceof between 500 and 1,500 ohmswithin the bore in the filling, means forconnecting one end of the resistance electrically to the high tensioncable, and means for connecting the other end of the resistanceelectrically to the central electrode of the sparking plug.

FRANK RAYMOND FABER RAMSAY.

